Monitoring circuit for logging instruments



June 9, 1964 R. H. KOLB MONITORING CIRCUIT RoR LoGGING INSTRUMENTS FiledJuly 20. 1959 l l I Pmv INVENTOR ROBERT H. KoLB BKL/1W TMW HIS ATTORNEYUnited States atent lice 3,136,975 MONITORING CIRCUIT FOR LOGGINGINSTRUMENTS Robert H. Kolb', Houston, Tex., assignor to Shell OilCompany, a corporation of Delaware Filed July 20, 1959, Ser. No.823,2tl8 3 Claims. (Cl. 34018) This invention pertains to a monitoringsystem and more particularly to a system which is designed to monitor adevice and its associated circuit as it is being installed 111 an oilwell or the like.

Many devices are semi-permanently installed inthe bottom of oil wellsand the like for determining various physical properties. For example,pressure and temperature transmitters are installed in the bottom of oilwells and connected to surface recording equipment by a connectingcable. As these devices are being installed in oil wells they receiveconsiderable mechanical shock and thus often times either the device orits associated In some installations the downhole tion tubing string.Normally the damage is not discovered until after installation iscompleted and an attempt is made to obtain information such as downholepressure or downhole temperature from the device which has beeninstalled. Since the damage is not discovered until after theinstallation is completed and the rig has been removed from the wellconsiderable expense is involved in retrieving the device, correctingthe trouble and reinstalling it. The cost involved is readily apparentwhen it is remembered that the average oil well in the United States ison the order of 7,000 to 10,000 feet deep lvice and its associatedcircuit and periodically indicate the condition'of the ldevice and itscircuit as the downhole instrument is being installed.

A further object of this invention is to provide a small lcompactautomatic monitoring system which audibly indicates the condition of thedownhole device and its associated circuit during its installation inthe wellbore without requiring either manual attention or observation.

The above objects and advantages of this invention are obtained byproviding a device which will periodically interrogate the downholedevice and its associated circuit yand receive a return responseindicating the condition of the downhole device and its circuit. Theresponse of the device to the interrogation is amplitied and passedthrough an audio speaker so that an audible sound-orringing will beobtained. Thus, if the device is interrogated at set time intervals anassociated audible sound will be produced. The people associated withthe installation will only be required to listen for the audible soundand not required to check or initiate any tests in order to determineWhether the device and its associated circuit is in a satisfactoryoperating condition.

The above objects and advantages will be more easily understood from thefollowing detailed description of a preferred embodiment when taken inconjunction with the attached drawing showing a schematic diagram ofthis invention as applied to a downhole pressure transmitter.

Referring to the attached drawing, there is shown a downhole pressuretransmitter 10, a pulsing circuit 11 and an amplifying circuit 12. Thedownhole pressure transmitter may be of any design such as the oneillustrated and described in the applicants copending application,Serial No. 731,328, filed April 28, 1958 and now Patent Number3,062,052. This typeof transmitter utilizes a vibrating string whosefrequency varies with pressure. It is interrogated by drawing the stringto one side by means of a coil and armature and then releasing thestring, the

.vibrations of the string inducing an alternating signal in the coil.This invention is designed to periodically test the operation of thedownhole pressure transmitter 10 and the cable 14 in order to ascertainthat itis in a satisfactory operating condition during its installationin a well. The surface equipment generates a periodic pulse which istransmitted down the cable 14 to interrogate the transmitter 10 and thenaudibly reproduces the transmitter response. The surface equipment alsoaudibly reproduces the interrogating pulse thus indicating that thesurface equipment is operating satisfactorily and has actuallytransmitted a pulse tothe transmitter 10.

As shown on the drawing, the pulsing circuit 11 utilizes a variableresistor 20 in series withA a fixed resistor 21 and a capacitor 22 as aresistance capacitor circuit for determining theA period betweenindividual-pulses. The variable resistor 20 and fixed resistor 21 arein'series with a second fixed resistor 27 which forms part of a secondresistance capacitance circuit. The resistance capacitor circuit iscoupled by means of a lead 25 to the positive side of a battery 23 whosenegative side is grounded at 24. Thus, the capacitor 22 will be chargedexponentially to a final voltage which is determined by the reakdownvoltage of the diode 26. More particularly, the diodes 26 and 32 arefour-layer, two lterminal semiconductor devices. The diodes 26 and 32have the particular quality of acting as a switch in that they remainopen and exhibit a relatively high resistance until a predeterminedvoltage level is exceeded at which level they break down and exhibit arelatively low resistance thus acting as a switch. In a particularcircuit the resistances 20 and 21 have a value of approximately 50,000ohms and the capacitor 22 a value of 100 microfarads, the resistance 27having a value of approximately 80 ohms, and the diode 26 having abreakdown voltage of 30 volts. Thus, the capacitor 22 will be chargeduntil it reaches a voltage level of 30 volts at which point the diode 26will break down and the capacitor discharge through the remainder of thecircuit to the ground 24. If the resistance 20 is provided with asuitable range one may obtain a charging time for the capacitor 22 onthe order of 10-15 seconds and thus the period of the pulse may bevaried between these limits. f

After the diode 26 breaks down and permits the capacitor 22 to dischargethrough the remainder of the circuit, the capacitor 31 will be chargedto the breakdown voltage of the diode 32. The capacitor 31 is in serieswith the resistance 27 and thus forms a second resistance capacitancecircuit. The capacitance 31.is connected to the ground 24 by means ofleads 44 and 45. The diode 32 is selected so as to have a lowerbreakduration. This pulse is coupled to the center conductor' 40 of thelogging cable 14 by means of a current limiting resistor 30, the lead34, diode 35 and lead 36. The

pull stage being` coupledto a speaker lfthrough an outputtransformer 60.`As shown, the transistors of the audio amplifier may be suppliedwithpower from a single diode 35 should be selected Vto have al certainthreshold v voltage on the order of one volt or the like.

Theshield or outer conductor r41 of the'logging cable .14 is connectedto the ground 44 by means of lead 42.V

A second diode 43 is disposed in the opposite direction to and parallelVwith diode 35 in order to provide al path to ground for the decreasingportion of the pulse as will be'explained below. i y Y When theabove-described pulsing circuit is operated by closing the switch 37 onthe battery 23 the capacitor 22 will charge as described above until thebreakdown Y voltage of the VVdiode 26 is reached. This voltage. level isapproximately 30 -volts for the example given above and'is reached inapproximately 10-15v seconds depend-V I ing Vonthe setting of theresistance 20. This voltage of when the diode 26 breaks down. When thediodev 26 breaks down it permits the capacitor l2,2 todischarge Vthroughthe remainderY of the pulsing circuit to the ground- 24, thus chargingVthe capacitor 31. As capacitor 31 charges it will generate anexponentially increasing volt-v age pulse at the point 33 having asubstantial instantaneous return to zero when the breakdown voltagelevel of the diode 32y is reached; This pulse kwill be transmitted :25course will have an exponential form well known in their. Tcharging ofacapacitor and a sharp decrease to'zero through the diode 35 in asubstantially unaltered form to the downhole pressure transmitter 10.,Itis desirable to use a pulsewhich has an` exponential wave form on itsforward side and a steep wave form 1on its back side,-

in contrast to a square wave pulse for actuatingthe downhole pressuretransmitterrlt). This results from 'Y' coupling the device to thesurface ofthe Well, a pulsing the fact that the pressure transmitter 10utilizesa vibratf ing string and if the string was Vpulled sharplyto-one side through rthel use of a pulse having a square Ywave shape thestring would vibrate in the displaced position and in case it wasreleased by the square wave pulse on the inward half cycle/of itsvibration the subsequent signal would have a greatly diminishedamplitude.

ing Voltage pulse since the string is slowly pulled towards the magnetthus preventing its vibration until-'it is released by the breakdown ofthe voltage pulse. t

The voltage pulse transmittedfover the cable 1.4 rises to a maximumvalue and then falls to zero. The diode 35 blocks the path to ground forthe falling pulse and thus the pulse tends to charge the cable 14,due toits capacitance. path to ground is provided by inserting' diodel43 Vvinparallel with and in opposite direction to the diode 35. This paththrough the Vdio'desg43 and 32 will permit the fallingv signal from thecable 14 to be bypassed tothe ground 24 and 'thus maintain the cablerelatively free of any charge. to ground it isolates thisV ground'pathfor the low amplitudel return signals from the'trarismitter because ofits threshold voltage and, thus the two diodes 35 and 43 act as a switchto couple thev pulsing circuit to the vcable 14V during'theY pulsingperiod and disconnect. it vduring the receiving period. f l Y The signalfrom the transmitter v10 is coupled tothe audio amplifier 12 through ablocking capacitor l50. The'r audio amplifier. 12 is providedwith threesingle stages This dificulty is avoided by using thel exponentiallyincreasf Even though the diode 43 provides 'aV path To prevent thisbuildup of a charge a battery 5'7k if so desired. v

`jFrom the above description it can-be' appreciated that Y thisinvention has provided a simple pulsing circuit which.'Y utilizes allsolid ystate elements to generatef periodic pulses for interrogating thepressure transmitter V10 and for connec'ting cable 14, as the pressuretransmitter is installed in a well. The kuse'fofisolidV stateelements'r'esults in aV very reliablefdevicewhich has relatively lowpower re-VA Y quirements. Furthermore, theperiod ofthe pulse may bevaried over VaY relatively-Wide range through the use Vof thevariable're'sistance 20. Also. the `pulse supplied for interrogating thepressure transmitter :10 hasan exponentially increasing forward sidewhichinsures thatV the audio signal ygenerated bythe vibratingA stringof the pressure transmitter will have a uniform amplitude.y Finally, theaudio amplilier V12 will audibly reproduce both the Vinterrogating pulsersupplied to thep'ressure transmitter as well as ltheau'dio signahfromthe pre`sV sure transmitter. Thus, the personinstalling th'efpres.-

sure transmitterwill iirst hear the iiterrogating pulse and` an instantlater the'pulse of theV pressure transmitter. If the interrogating pulseis not heardV i t indicates thatfthe n Y pulsing circuitis'malfunctioning: whi1e`if the int'er'ro-Vy gating pulse is heardbutnotthe audible signal fromthe pressure transmitter, it would indicatethat the cable Ycir-` cuit 14 or the pressure transmitterrlO ismalfunctioning. i Therefore, the invention audiblyV indicates both thefunctioning ofthe pulsing circuit and the(Y pressure transmit- ,ter andassociated circuit. 1 Y ,Y Y While but a single embodiment of thisinvention has been .shown and described-'in detailV it shouldnot beVlimited to the details described but only tov its'broad spirit 1 andscope;

jI claim asV my invention: Y Y

1. A system yfor monitoring the installation in .a-wellboreV o'f avibrating string device ycapable of'measuring a physical characteristic,said system comprising: a cable age; said secondcapacitance'resistance-circuit having a .n relativelyshort'rtimeconstant Vand coupled to ground throughk a secondA static device havinga predetermined breakdown voltage; saidsecond capacitanceresistancecircuit being coupled to said cable througha diode totransmitv the pulseproduced by'said second capacitance resistance circuit; to energizethedevice saidk cable in additionV beingcoupled to an amplifier andk audioVreproducing means located at the Vsu'rfacefto reproducebo'th Y saidypulseand the responseof the device.

2.L A system for monitoring thef installation in a Wellbore `of avibrating string device capable of measuring a physical quantity; saidlsystem comprising: a-cable coupling the device toV the surface of thewell,`"arpulsing I circuit locatedat the lsurface and having a lfirstcapaci-- V,tance "resistance circuit having an adjustable time Icon-VVstant, ysaidy capacitance resistance circuitbeing coupled .to a secondVcapacitance resistancecircuit through a :iirst static device havingapredetermined breakdown voltage; said second capacitance resistance,circuit having a relative short time constant and coupledto ground,through a second static device Vhaving afpredetermined breakformed bytransistors 51, 52 and 53 anda push-pull out- I put stage-formed bytransistors 55 and 56.' The output of transistor 53 is coupled to thepush-pull output stage n through a transformer54 with the outputfrom thepushsistance circuit to energias its device; saidl cable inadj dition:being coupleditolanaudio amplifieriandspeaker system located at the'`surface to reproduce both ksaid pulse and the response of the deviceianda secondV dioder Y disposed in parallel with but opposite to said lirstdiode to provide a path to ground.

3. A system for monitoring the installation of a de vice in a Wellborecomprising: a cable coupling the device to the surface of the Well, saiddevice supplying an audio frequency signal when interrogated by a pulseof sucient magnitude; a pulsing circuit including a first means forgenerating a periodic pulse having a preset repetition rate, a secondmeans energized by the pulse of said first means for generating a secondpulse capable of interrogating the device; unidirectional circuit meansfor coupling the second pulse to said cable and another circuit meanscoupling the response of the device to an amplier means whereby thedevice is interrogated and both the second pulse and audio frequencysignal from the device are audibly reproduced.

References Cited in the le of this patent UNITED STATES PATENTS KinleyIan. 3, OBrien May 27, Schultz Nov. 16, Martin Nov. 14, Thomas Aug. 17,Atkinson Nov. 30, Curtis Jan. 10, Summers Mar. 6, Aigrain July l5,Rumble Dec. 1, Mason Apr. 18, Ruehlemann Sept. 5,

1. A SYSTEM FOR MONITORING THE INSTALLATION IN A WELLBORE OF A VIBRATINGSTRING DEVICE CAPABLE OF MEASURING A PHYSICAL CHARACTERISTIC, SAIDSYSTEM COMPRISING: A CABLE COUPLING THE DEVICE TO THE SURFACE OF THEWELL, A PULSING CIRCUIT LOCATED AT THE SURFACE AND HAVING A FIRSTCAPACITANCE RESISTANCE CIRCUIT HAVING AN ADJUSTABLE TIME CONSTANT, SAIDCAPACITANCE RESISTANCE CIRCUIT BEING COUPLED TO A SECOND CAPACITANCERESISTANCE CIRCUIT THROUGH A FIRST STATIC DEVICE HAVING A PREDETERMINEDBREAKDOWN VOLTAGE; SAID SECOND CAPACITANCE RESISTANCE CIRCUIT HAVING ARELATIVELY SHORT TIME CONSTANT AND COUPLED TO GROUND THROUGH A SECONDSTATIC DEVICE HAVING A PREDETERMINED BREAKDOWN VOLTAGE; SAID SECONDCAPACITANCE RESISTANCE CIRCUIT BEING COUPLED TO SAID CABLE THROUGH ADIODE TO TRANSMIT THE PULSE PRODUCED BY SAID SECOND CAPACITANCERESISTANCE CIRCUIT; TO ENERGIZE THE DEVICE SAID CABLE IN ADDITION BEINGCOUPLED TO AN AMPLIFIER AND AUDIO REPRODUCING MEANS LOCATED AT THESURFACE TO REPRODUCE BOTH SAID PULSE AND THE RESPONSE OF THE DEVICE.